Binks model#33-566 valve leaking air

by Rick
(Duncan B.C. Canada)

My Binks model#33-566, serial#310-22, takes a while to build air pressure(0 to 150 lbs. in 35 minutes). After shutting down, a puffing sound every 3 seconds is heard thru the intake. I believe it is leaking past the valve(s). It takes a 2-3 of days to drain the 80 gallon tank. I would like to know which valve is leaking, and how to remove, clean/or rebuild, gaskets,and any other pertinent info on the matter would be appreciated.